/Engine/Source/Runtime/Renderer/Public/MeshPassProcessor.h
Container for primtive ID info that needs to be passed around, in the future will likely be condensed to just the instance ID.
struct FMeshDrawCommandPrimitiveIdInfo
uint32:  1
bIsDynamicPrimitive
Set to true if the primitive ID and instance data offset is a dynamic ID, which means it needs to be translated before use.
int32
DrawPrimitiveId
Draw PrimitiveId this draw command is associated with - used by the shader to fetch primitive data from the PrimitiveSceneData SRV.
int32:  31
InstanceSceneDataOffset
Offset to the first instance belonging to the primitive in GPU scene.
int32
ScenePrimitiveId
Scene PrimitiveId that generated this draw command, or -1 if noFPrimitiveSceneInfo. Can be used to backtrack to theFPrimitiveSceneInfo.